Oil-controlled camshaft phasers are known in the art. Such devices allow camshaft timing to be continuously adjusted by a closed loop control system. Usually, actuation is controlled by engine oil, which is ported to the phaser at a control pressure. The actual phase angle of the camshaft with respect to the crankshaft is determined by means of sensors which monitor both crankshaft and camshaft position in real time. Oil is caused to be directed by a control valve to either a retard port or an advance port of the phaser to achieve the necessary adjustment in camshaft position. It is known to run oil through camshaft itself to achieve adjustment. U.S. Pat. Nos. 5,138,985 and 6,026,772 disclose systems in which oil is run about the camshaft itself. Each of the systems of the '985 and '772 patents are characterized by very large camshaft diameters in the area in which the oil is furnished to the camshaft phaser. Also, these designs rely on passages which are machined into the interior of the camshaft, and this presents problems because axial drillings are difficult both to machine and to clean after the machining process. Unfortunately, the presence of foreign material may cause a camshaft phaser to fail.
The present system uses a sleeve and axially directed grooves machined through the surface and into a subdiametral portion of the camshaft. The grooves and sleeve, taken together make up axially directed oil control passages.